This research will extend and hopefully conclude our investigations into the structural and metabolic relationships of the multiple forms of ferritin found in most mammalian tissues. The proposed research has two major, but related, objectives. The first is to define the structural differences in ferritin subunits and to relate these to the observed structural, immunological, functional and metabolic differences in isoferritins. The other is to elucidate the mechanism of ferritin induction by iron and the factors that regulate ferritin phenotypes in normal and malignant cells. Most of the structural work will be done with human and horse ferritins. Both consist of two distinct, but probably related subunits, H and L of approximately MR 21,000 and 19,000 respectively. These are produced in different proportions in different tissues to form families of heteropolymers. The H and L subunits from both species will be characterized more fully to identify sequence differences. This will be done by isolating unique peptides to each subunit and by conventional automated sequence analysis. Heteropolymer formation and subunit packing will be examined in reconstitution experiments with free subunits and by cross-linking experiments. Factors regulating the synthesis of both subunit types will be investigated in heterologous translation systems and by cDNA hybridization techniques. These studies will include-the mode of action of iron in inducing ferritin synthesis, assessment of ferritin H and L mRNA distributions in nuclear and cytoplasmic compartments, analysis of possible processing or glycosylation of subunits, attempts to separate and quantitate mRNA species coding for the H and L subunits. Most of these studies will use rat liver or hepatoma as source of mRNA.